Resonant-tunneling diodes (RTDs) having a GaAs/AlAs quantum well structure or an InGaAs/AlAs quantum well structure are quantum effect devices that have negative differential resistance characteristics, allow high-speed switching operation, and operate at room temperature. Multipliers, frequency dividers, sampling circuits, and multi-valued logic circuits using negative differential resistance characteristics have been developed. In particular, terahertz oscillators including RTDs have been increasingly developed in recent years, and application of RTDs to, for example, terahertz communication and image sensors is expected.
Recent studies have also focused on RTDs having a GaN/AlGaN quantum well structure (hereinafter may be referred to as GaN-based RTDs) that may be integrated with GaN-based high-electron mobility transistors (HEMTs).
However, GaN-based RTDs exhibit asymmetric I-V characteristics due to an internal field generated by polarization that is characteristic of GaN. Even if the Fermi level is aligned with the quantum level as a result of the raising of the conduction band on an emitter side, electron tunneling is difficult. Thus, a high-speed logic gate monostable-bistable transition logic element (MOBILE) circuit integrating a GaN-based RTD and a GaN-based HEMT fails to have good I-V characteristics.
Although various studies have been conducted to obtain symmetric I-V characteristics of GaN-based RTDs, GaN-based RTDs that may be integrated with GaN-based HEMTs to provide good I-V characteristics have not been obtained.
The following documents are reference documents.
[Document 1] Japanese Laid-open Patent Publication No. 2014-63917,
[Document 2] Japanese Laid-open Patent Publication No. 2005-79417,
[Document 3] Sakr et al., “Ballistic transport in GaN/AlGaN resonant tunneling Diodes”, Journal of Applied Physics, 109, 023717 (2011),
[Document 4] Lee et al., “In situ measurements of the critical thickness for strain relaxation in AlGaN GaN heterostructures”, Applied Physics letters, 85, 6164 (2004),
[Document 5] M. Park et al., “Micro-Raman study of electric properties of invention domains in GaN-based lateral polarity heterostructures”, Journal of Applied Physics, Volume 93, Number 12, 15 Jun. 2003, and
[Document 6] M. H. Wong et al., “Polarity inversion of N-face GaN by plasma-assisted molecule beam epitaxy”, Journal of Applied Physics, 104, 093710 (2008).